Pulse modulating control device with improved contact structure

ABSTRACT

An electromechanical pulse width modulation device for controlling torque, rotational speed and direction of rotation of a direct current electric motor, such as a series, shunt or compound wound motor. The device includes a rotary switch having pairs of brush contacts which are selectively electrically connected through engagement with conductive segments on a driven cylindrical commutator member. The brush contacts are adapted to intermittently connect a direct current source to the field and armature windings of the electric motor, with one pair of contacts being movable relative to the other pair in a manner to modulate the direction and duration of pulse signals from the switch to the field and armature windings of the motor.

United States Patent [72} Inventor Howard C. Hansen Battle Creek, Mich. [21] Appl. No. 706,417 [22] Filed Feb. 19,1968 [45] Patented Jan. 19, 1971 [73] Assignee Clark Equipment Company a corporation of Michigan [54] PULSE MODULATING CONTROL DEVICE WITH IMPROVED CONTACT STRUCTURE 13 Claims, 13 Drawing Figs.

[52] US. Cl 200/24, 310/230; 318/256, 318/281 [51] Int. Cl...... ..l-10lh 39/00 [50] Field otSearch 200/8, 19, 20-26, 166D. 166135. 166B6; 318/65, 202, 256, 280, 291, 292, 293; 310/230, 241 [56] References Cited UNITED STATES PATENTS 1,501,558 7/1924 Hunt 310/230X 2,500,571 3/1950 Reynolds.... 310/230 3,440,465 4/1969 Pratt et al. 310/230 2,416,229 2/1947 Shoemaker 318/281 2,424,859 7/ 1 947 Shoemaker 318/256 2,723,319 11/1955 S'eibring et a1 200/25 2,756,293 7/1956 Bitle'r 200/25 3,089,074 5/1963 Vaughan 317/100X 3,247,334 4/1966 Sebring 200/25X 3,434,014 3/1969 Taynton 3 l 7/100X Primary Examiner-Robert K. Schaefer Assistant Examiner-J. R. Scott, Jr. Attorney-Johnson, Dienner, Emrich, Verbeck & Wagner ABSTRACT: An electromechanical pulse width modulation device for controlling torque, rotational speed and direction of rotation of a direct current electric motor, such as a series, shunt or compound wound motor. The device includes a rotary switch having pairs of brush contacts which are selectively electrically connected through engagement with conductive segments on a driven cylindrical commutator memberv The brush contacts are adapted to intermittently connect a direct current source to the field and armature windings of the electric motor, with one pair of contacts being movable relative to the other pair in a manner to modulate the direction and duration of pulse signals from the switch to the field and armature windings of the motor.

pmtmingmsmn 3,557,325

' summon I INVENTOR HOWARD -c. HANSEN BY Ma ATTORNEYS PATENTED JAN 1 9 |97l snmznr 7 INVENTOR HOWARD C. HANSEN BY fiat, MW

ATTORNEYS PATENITEDIJANI 9 Ian sum 3 or 7 INVEN'IOR HOWARD C. HANSEN M M I v M m ATTORNEYS PA'TFNTFUJAINI 91am v I 3,15 3 25 I 'SHEETMOF 7 INVENTOR HOWARD C HANSEN ATTORNEYS mm m a; 557,325 smear-7 F G- I *{llllllf INVENTOR HOWARD c. HANSEN ATTORNEYS v PULSE MODULATING CONTROL DEVICE WITH IMPROVED CONTACT STRUCTURE BACKGROUND OF Ti -IE. INVENTION The present invention relates to pulse modulating control devices, and more particularly to electromechanical pulse modulating devices for'use in controlling the torque. rotational speed and direction of rotation of series, shunt or com pound wound electric motors. I

- In the use of electric motors to effect movement of devices such as material handling trucks. electric automobiles. golf carts and the like. it is desirable to provide a control arrangement whereby-the operator may control the speed of the device in both forward and reverse directions. Known methods for effecting control of electric-vehicles and other electrically powereddevices through controlling electrical input pulses to the device are so complex and. correspondingly costly as to prohibit their use in vehicles of modest cost. Moreover, repair and adjustment of the known pulse controlled devices require expensive test equipment and highly trained personnel. In additiomthe known methods for achieving control ofelectric motors through employing electrically resistive devices. of either fixed or variable resistance-are wasteful of electrical energy from the voltage source and thereby further add to their expense. 1

SUMMARY OFTHE mveNnoN It is one ofthe primary objects of the present invention to provide an efficientand novel electromechanical pulse control arrangement for simply and reliably effecting pulse. width modulation control of series, shunt and compound wound electric motors in forward and reverserotational directions.

' Another object of the present invention is to provide an electromechanical pulse control arrangement employing an electrically driven rotary switch having first and second. pairs of brush contacts which cooperate with conductive segments. ona driven cylindrical commutator-member to electrically connect'a direct current voltage source to the field and armature windings of an electric motor, with one pair olbrush contacts being controllably movable relative to the other pair in a manner to reverse the direction of current pulse through the field or annature winding of the motor to reverse the direction of rotation of the motor.

Another object of the present invention is to provide an electromechanical pulse control arrangement as described wherein the movable pair 'of' brush contacts is selectively movable about the driven cylindrical commutator member in a manner to establish rapid current pulses to the motor, with such movement being controllable to establish a desired ratio of ontime to ofi'time of the current pulses and thereby control as J the torque and rotational speed of the'motor in either rota- I trically connected in a manner to double the current capacity of the modulating device for controlling largerelectric motors. the brush contacts being selectively connected through conductor segments to provide parallel current paths through the modulating device.

In one embodiment of a pulse modulating control arrangement in accordance with the present'invention. for use in controlling thetorque, rotational speed and direction of a series wound electric motor, movable and fixed pairs of brush con- 75 tacts are disposed for sliding engagement with a driven cylindrical commutator member having conductive elements disposed. about the periphery thereof. The conductive elements are adapted to conductivcly couple a movableand a fixed brush contact during each revolution of the commutator member, with the movable brush contacts being movable-relative to their corresponding fixed contacts in a manner to vary the time duration of electrical pulses through the respective pairs of fixed and movable contacts. The rotary switch including the driven commutator and brush contacts is connected in circuit with a direct current voltage source such that current pulses are established through the field and armature windings of the motor. the brush contacts being adapted to establish a reversccurrent llow through the field windings to thereby reverse the direction of rotation of the motor.

An alternative embodiment of ajpulse' modulating control arrangement in accordance with the present invention connects selected pairs of brush contacts of the rotary switch such that current pulses pass through the rotary switch in two parallel paths. The two parallel current pulses are recombined after passing through the rotary switch and thereafter connected to the motor armature and field coils; When providing parallel current pulse paths throughthe rotary switch device for use with a large size electric motor, a conventional reversing contactor switch is employed to effect reversecurrent pulse flow through the field winding and thereby reverse the rotation of the motor. I 1 I Other objects, features 'andadvantages of my invention will become apparent from the following description of preferred embodiments when taken in-conjunction with the accompany- BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of an electromechanical pulse modulating control arrangement in accordance with the present invention operatively associated with a material handling truck;

FIG. 2 is a schematic view, in perspective. of the rotary switch of the control arrangement illustrated in FIG. I showing the conductive elements on the driven cylindrical commutator member and pairs of brush contacts disposed in neutral nonconducting positions; I

FIG.) illustrates schematically the rotary switch oi FIG.'2 in circuit with a voltage supply and the armature and field windings of a series wound electric motor;

FIG. 4 is a longitudinal cross-sectional view of an alternative embodiment of a rotary switch in accordance with the present invention employing a driven cylindrical commutator member and brush contacts, with means being provided for eltecting angular displacement of the movable brush contacts relative tothc fixed brush contacts; 7

FIG. 5 is a schematic view, in perspective. of the alternative rotary switch of FIG. 4 with the driven cylindrical commutator and conductive elements in operative association with brush contacts disposed in neutral nonconducting positions and with the drive motor for the commutator removed;

FIG. 6 illustrates schematically the rotary switch oi FIG. 4 in circuit with a direct current voltage source and a (his en DC electric motor. the movable brush contacts being snown in neutral nonconducting positions in solid lines and conducting.

positions in dash lines; o

. FIG. 7 illustrates a further embodiment of an electromechanical pulse modulating control arrangement in accordance with the presentinvention wherein a rotary switch device as illustrated in FIG. 2 is connected in circuit to provide parallel current pulse paths through the switch device, the rotary switch being used to control a series wound DC electric motor;

FIG. 8 is a schematic circuit diagram similar to FIG. 7' but illustrates the rotary switch connected in circuit to control a shunt wound DC motor;

-against' 't'he inner peripheral surfacethereof. certain of the brushes'being angularly movable relative to fixed brush con- FlG. 12 is a transverse sectional view taken substantially along the line 12-12 of FIG. 11 looking in the direction of the arrows; and

FIG. 13 is a transverse sectional view taken substantially along the line 13-13 of FIG. 1 ,lool ing in the direction of the arrows. f

; ipigscR rrio in THE PREFERRED EMBODIMENTS the below described preferred embodiments of the subject invention are illustrated in conjunction with the control of a material handling lift truck, it will be understood that the basic concepts underlying the present invention find ready application .in controlling any electrically driven or energized device wherein .itgis desired to establish pulse modulation of an electrical input; signal thereto. In all electrical "circuits described he'reinbelow in which the pulse modulating device according to the present invention is employed to control series wound electric motors. appropriate electronic circuitry to suppress'arcing at the brush contacts is preferably employed.

Referring'now to the drawings, and in particular to FIG. 1. an electromechanical pulse modulating control arrangement in accordaricewith one embodiment of the present invention is indicated 'generally at reference numeral in operative association with a material handling hand truck 12. The hand truck -12 is, of conventional design and includes a pair of outwardly extending support arms of fork members, one of which is shown at 14, which serve to support a load or material supporting pallet during transportation thereof. A steering shaft 16 is provided on the rear portion of the hand truck 12 in a position to be readily maneuverable by an operator for purposes of steering the truck. A single drive wheel (not shown) is disposed within a re'aicasing portion 18 and engages the ground or floor for purposes of driving the vehicle and steering'the same inaconventional manner. The hand truck 12 includes 'agnerallyupstanding casing or housing portion 20 serving to enclose a conventional direct current electric motor such as a series, shunt"o r, compound wound DC electric motor (not shown) which may be directly coupled to the drive wheel. The housing20 further serves to enclose a power supply for the electric drivemotor whichlrnay the form of a bank of batteries or other suitable direct current voltage source (not shown) charged to provide a direct'current energy source for the electric drive motor,

The pulse modulatingc ontrol arrangementlO is supported on a mounting plate 22 which in turn is supported on the upper surface of the casing or housing 20 of the hand truck. The pulse control-arrangement 10 includes a pulse modulating device taking the form of-a rotary switch means, designated generally at referencenumeral24, which is coupled in circuit 'between the aforementioned voltage source and the electric drive motor and isoperable to selectively modulate the current input signal frorn'the voltage. source to the drive motor in a manner to be described hereinbelow.

The rotary switch means 24 comprises a housing member having two axially aligned portions 26 and 28 which have generally cylindrical outer'peripheral-configurations and are supported between a pair of upstanding support plates 30 and 32. The upstanding support plates 30 and 32 may be suitably the c secured to the plate member 20 and in any conyentional manner such as throughboItsS LThe respective housing portions 26 and 28 of the rotary switch means 24 are supported so as to bc rotatable relative to each other with the housing portion 26 being preferably fixedly supported on the support plate 30 in any suitable manner. The housing portion 28 may be coupled to housing portion 26 at interface 36 in a manner to allow relative rotational movement between the housing portions. or may be slightly axially spaced from the housing portion 26 with a sealing meanslnot shown) being coopera tivcly associated with the twofihousirig portions 26 and 28 as to preclude the introduction ofdust'or other foreign matter into the rotary'switcht The housing portion 28 may be suitably rotatably supported on the upstanding support plate 32 in any conventional manner, it being necessary that the housing portion 28 be freely rotatable relative to the support plate 32. Each of the housing sections 26 and 28 has an identical cylindrical axial bore 38 th'erethrough which forms .a continuous longitudinally extending bore to receive a rotatably cylindrical member 40 therein for rotational rriov'eme'nt within the cylindrical bore 38.-

Referring now to H6: "1 takeninconjunction with FlG TZ, "d 'caltrriember'40 may be supported for rotational movem 't within the cylindrical bore 38 by the respective housing portions-26 and 28. df the'switch means 24, or the cylindrical member 40 may. be rotatably supported in a conventional mannerby the upstanding support plates 30 and 32, it being merely necessarythat the cylindrical member 40 be "iotat'ably 'and concentrically disposed within the bore 38 of {the housing portions 26 and 28. The cylindrical member 40 is "-Eotata-bl y dtiven by a fractional horsepower direct current electric motor 42 which may be suitably mounted on the plate member 40.' The electric motor 42 has its drive shaft: 44

suitably coupled to the 'cylindrical member 40 so as to effect derstood that the means for couplingthe motor drive .shaft 44 to the cylindrical member 40, Eas -well as the means for rotatably supporting the cylindrical member 40 within the switch housing portions 26 and 28; maytake any of the-conventional forms known in the art, ,=it being merely a matter of mechanical expediency to select one preferred method of coupling or mounting over anothen' v 1 Each of the switch housing portions 26 and 28 inclu des a pair of diametrically opposed carbon graphite brush contact members 46 and 48, respectively, which may be of a conventional design and are disposed in generally radial relationv to the respective housing portions. The'contact members 46 and 48 are secured to the zresp'ective h'ousing portions such that the inner ends thereof engage the pcriphcral surface of the cylindrical member 40 in sliding contacmelation. The inner'contacting ends of the respective pairs'of contact members 46 and 48 are preferably concaveini crbss' section having a radius equal to the radius of the cylihdri'cal member 40 to insure good contact with member40fThe outer ends of the respective contact members 46 and 48 are conductively coupled through suitable conductor elements 50 and 52.respectively, in circuit with the primary voltage source and the electric drive motor, above described; in a manner to be described hereinbelow. I L

The movable housing portion 28 'of'the r'o'tary switch means 24 is provided with a' fnannular groove 64 in the peripheral sur-' face thereof which receives an endless chain or belt member 66 in frictional 'engage menttherewith for effecting rotational movement of the housing portion 28 of the rotary switch. The endless belt member 66 is also disposed in frictional relation about the peripheral edge surface'68 of an actuator wheel 70 which is rotatably supported by a support pin 72 in alocation conveniently accessible to the operator of the hand truck; The

actuator wheel 70 includes a pair of projecting handles or actuator rods 74 which facilitate rotational movement of the actuator wheel 70 by the operator. The actuator wheel'70 is disposed in a plane containing the annular groove 64'such that the endless belt member 66 will alsolie in the same plane. It can be seen that the operator may selectively effect rotational movement of the housing portion 28 of the rotary switch means 24 relative to the housing portion 26 through rotatable movement of the actuator wheel 70 and thus can vary the angular relationship between the respective pairs of contact members 46 and 48. 7 i

The cylindrical member 40 of the rotary switch means 24 has four circumferentially equidistantly spaced'conducting elements or segments 54 suitablysecured to the peripheral surface thereof such that the outer surfades 'of the respective conductor elements 54 lie in the peripheral surface of the cylindrical member 40. The conductive elements 54 have lengths substantially equal to the longitudinal length of the cylindrical bore 38 such that each conductive element 54 may conductively connect or couple one of the contact members 46 to an associated contact member 48 during rotational movement of the cylindrical member 40 as will be" more fully described hereinbelow. The. conductive elements 54 are preferably made of a conductive material. such as 'a copper bronze or the like, having good conductive and wear resistant properties. while the cylindrical member 40 is preferably made from a nonconductive .wear resistant material. Preferably. thewear resistant properties of the materials comprising the conductive elements 54- and the cylindrical member are substantially identicalto preclude the forma tion of wear grooves between the respective members during contact thereof with the contact members 46 'and 48. The circumferentialspacing between the respective conductive elements 54'is preferably made slightly greater than the circumferential widthiof the inner contact surfaces-of the contact members 46 and'48 such than when the planes of the respective pairs of contact members are disposed at right angles to each other.-with the contact members 46 disposed between adjacent conductive elements as shown in FIG. 2, the-contact members 48 will also be disposed between adjacent conductive elements. In this position, the conductive elements 54 will only contact one of the contact members 46 or 48 at a time as the cylindrical member 40. is rotated through one revolution, thusprecluding conductive coupling between any two of the contact members 46 ancl48.

Referring now to FIG. 3. an end view of the rotary switch means 24 is illustrated schematically, connected in circuit with a direct current voltage source 56 which, as noted above, may comprise a bank of batteries or other suitable source encased within'the housing 20 of the hand truck I2-The voltage source 56 is connected to an armature winding 58 of an elecmovement-of the hand truck l2.The' armature winding 58 is connected by a conductor 52 to. one of the movable contact members 48. The diametrically opposite contact member 48 is connected through a similar conductor 52 to theground terminal of the voltage source 56..The outer ends of fixed position contact members 46 of the rotary switch means 24'are connected through their respective conductors 50 to the ends of a field winding 62- which is operatively associated with the armature winding 58in a conventional manner to form the series wound direct current-drive motor.

Having thus described the elements comprising one embodiment of an electromechanical pulse modulating control arrangement in accordance with the present-invention, its

operation will now be briefly described. Referring to FIGS. L

-3, it can be seen that when the movable contact members 48 I member 40 will conductively connect one of the movable contact members 48 to one of the fixed position contact members 46 once during each revolution of the cylindrical member 40. Selective rotational movement of the movable contact members 48 is effected through rotational movement of the housing portion 28 of the rotary switch means 24 through the actuator wheel 70 as above described. For example. when the movable contact members 48 are rotated in a counterclockwise direction away from their l'IOIlCOI'ItlUCllVC positions to a position as illustrated in solid lines in FIG. 3. an input pulse signal from the voltage source 56 will be established through the armature winding 58. the associated movable contact member 48. the corresponding conductive element 54 which is nowconductively connecting the movable contact member 48 to a corresponding fixed position contact member 46', through the field winding 62. and through the opposing pair of contact members 46 and 48 and their associated conductive element 54 to the ground side of the voltage source 561 .45 there are four'conductive elements 54 provided on the cylindrical member 40, it can be seen that the aforedescribed input pulse through the armature winding SS and field winding 62 will be established four times for each revolution of the cylindrical member 40. The input pulses thus established through the motor armature and field windings will effect rotational movement of the drive motor and thereby movement of the hand truck 12 in either a forward or reverse direction depending on the mechanical coupling between the motor and the drive wheel.

Having established a rotational movement of the electric motor in a first direction as above described, it may be desired to reverse the direction of the motor and thus the direction of travel ofthe hand truck. To accomplish such reversal. the contact members 48 are rotated in a clockwise direction, when viewing FIG. 3, by the actuator wheel 70 and endless belt 66- Ma position as in dash lines in FIG. 3. With the movable contact members 48 rotated in a clockwise direction, it can be seen that the input pulse from the voltage source 56 will now be through the armature 58, the first movable contact 48 and its associated fixed contact member '46, and thereafter through the field winding 62 and back to the ground terminal of the voltage source 56. In the last described position,.the direction of current flow through the motor field winding 62 will be reversed to that initially described. The reversed cur-' rent flow through the field winding 62 will effect a reverse in the rotational direction of the electric drive motor thus effecting a reversal in the direction of travel of the hand truck 12.

The time duration of each current impulse signal through the respectiveassociated pairs of movable and fixed contact members 48 and 46 depends upon the angular positions of the movable contacts 48 relative to the plane of fixed contacts 46,

the circumferential width of each of the conductive elements 54in the peripheral surface of the cylindrical member 40, and

.the rotational speed of member 40. The frequency of such' input pulses may be varied by varying the rotational speed of thc'cylindrical member 40, this beingdetermined by the electric' motor42. The'pulse modulating control arrangement 10 thus provides a means for controlling'thc torque, rotational speed and direction of rotation of the truck drive motor.

Referring now to F IGS. 46, an alternative embodiment of an electromechanical pulse modulating device, shown generally at reference'numeral 8 0, is illustrated which may be readily adapted for use with the above described material handling hand truck [2 to control the torque and rotational speed of its drive motor. The pulse modulating control device may replace the above described rotary switch means 24 and preferably is used with conventional electric motor reversing contractor means.

The pulse modulating control device 80 comprises a rotary switch having a housing defined by a generally annular outer shell 82'and end plates 84 and 86 suitable secured thereto as through bolts 88. The end plates 84] and 86 are disposed in parallel spaced relation and having centralfaxially aligned apertures 90 and '92, respectively, therethroughwliichserve to receive and rotatably support a cylindrical commutator 94 through conventional antifriction bearings 96.

The cylindrical commutator 94 has reduced end portions 98 and 100 which receive the bearings 96 thereon. The end portion 100 of commutator 94 is adaptedto be suitably coupled to a fractional horsepower electric drive motor (not shown) for high speed rotation of the commutator. The cylindrical commutator 94 comprises a cylindrical body portion made of a dielectric material and has two arcuate copper conductive commutator segments or elements 102 and 104 suitably embedded or otherwise secured thereon such that the outer peripheral surfaces of the arcuate conductive elements are coincident with the outer peripheral surface of the cylindrical body portion. Noting FIGS. and 6, the arcuate extent of each f the commutator conducting elements 102 and 104 is made less than 180", with the conductive element 104 being angularly displaced about the circumference of the cylindrical body 94 relative to conductive element 102 as will be described more fully hereinbelow. The conductive elements 102 and 104 are axially spaced on the cylindrical commutator 94, with each of the conductive segments having a length of approximately one-half the length of the portion of the commutator disposed between the end plates 84 and 86 of the rotary switch housing.

A pair of carbon graphite brush contacts 106 and 108 are supported by the annular housing shell 82 in fixed arcuate position while allowing radial movement thereof relative to the axis of rotation of the commutator 94. The brush contacts 106 and 108 are suitably guided for such radial movement by sleeves 110 and 112, respectively, disposed about the peripheral surface of each of the brush contacts and secured in electrically isolated fashion within appropriate apertures in the annular housing 82. A pair of electric connector lugs 114 and 116 are supported by annular housing shell 82 adjacent the brush contacts 106 and 108, respectively, and are electrically insulated from the guide sleeves 110 and 112. respectively. The connector lugs 114v and 116 are suitably electrically connected to their respective brush contacts 106 and 108 through conductor wire means 118. The brush contacts 106 and 108 are urged radially inwardly by suitable coil springs 120 to engage the peripheralysurface of the cylindrical commutator 94'and the commutator conductive elements 102 and 104, the brush contact 106 being disposed for sliding contact with conductive element 102. while the brush contact 108 is disposed for sliding contact with the conductive element 102.

A second pair of carbon brush contacts 122 and 124 are supported within the rotary switch housing for angular movement about the axis of rotation of the cylindrical commutator member 94. The brush-contacts 122 and 124 may be su ported for such angular movement in any suitable manner, FIG. 4 illustrating the brush contacts 122 and 124 as being supported on annular support brackets 126 and 128, respec-' tively, which in turn are supported on bearings 130 for rotation about the axis of rotation of the commutator 94. To effect rotation of support brackets 126 and 128, a chain means 132 is provided which is guided through tubular. guides 134 and has end portions connected to the annular support brackets. Longitudinal movement of the chain means 132 through an exterior source (not shown) in either an inward or outward direction will effect simultaneous rotational movement of the annular supportbrackets 126 and 128 and thereby a similar angular displacement of the brush contacts 122 and 124 about the commutator cylinder 94.

The brush contacts 122 and 124 are slidably disposed within guide sleeves 134 and 136, respectively, which in turn are suitably secured to the respective annular supportbrackets 126 and 128. The guide sleeves'132 and allow radial movement of the brush contacts 122 and,124 relative to the commutator cylinder 94, with the brush contacts being urged inwardly through suitable coil springs 138.

A connector lug 140 is suitably supported by the annular housing portion 82 so as to be electrically insulated therefrom and serves as a connector means for connecting the brush contacts 122 and 124 in circuit through conductors 142.

Referring to H6. 6. the commutator 94 and conductive brush contacts 106, 108, I22 and 124 are shown schematically in circuit between a direct current voltage source 146 and a series wound electric drive motor. shown diagrammatically at 148. The circuit is comprised oftwo parallel branches. A first circuit branch includes the fixed brush contact 106, the movable brush contact 122 and the conductive element 102 of commutator 94. The fixed brush contact 106 is connected to the positive terminal of the DC voltage source 146 through a conductor 150, and the movable brush contact 122 is connected to the drive motor 148 through a conductor 152. The second branch of the circuit includes the fixed brush contact 108, the movable brush contact 124'and the corresponding conductive -element 104-of the commutator 94. The fixed brush contact 108 is connected to the positive terminal of the voltage source 146 through a conductor 154 and the movable contact 124 is connected to the electric motor 148 through conductor 152. The series wound electric motor 148 is suitably connected to the ground terminal of the voltage source 146 through a conductor 156. A suitable electrical arc suppression means 158 is connected in parallel with the drive motor 148 across the conductors 152 and 156.

The operation of the electromechanical pulse modulating control arrangement illustrated schematically in FIG. 6 is as follows. With the fixed and movable brush contacts 106 and 122, respectively. positioned on diametrically opposite sides of the cylindrical commutator 94 as shown in solid lines, no current will flow from the voltage source 146 to the electric motor 148. as the arcuate extent of conductive element 102 prevents conductive connecting of the brush contacts. Similarly. when the fixed and movable brush contacts 108 and 124, respectively, are in diametrically opposed positions as shown in solid lines, element 104'will not conductively connect brush contacts 108 and 124. Thus. when the brush contacts are in their diametrically opposed positions, the electric drive motor 148 will not be energized. Angular movement of the movable brush contacts 122 and 124 through the above described chain means 132 topositions as'shown in dotted lines in FIG. 6, will allow pulse conduction from the voltage source 146 to the electric motor 148. For example, when the commutator cylinder 94 is in a position such that the conductive elements 102 and 104 are in the positions shown in dash lines. the element 102 will initiate a pulse input to the electric motor 148 throughout the duration of its contact with both brush contacts 106 and 122. Prior to the conductive element 102 terminating its contact with both brush contacts 106 and 122, the conductive element 104 will connect brush contacts 108 and 124 and thereby sustain the impulse signal to the electric motor 148 until the commutator cylinder 94 is rotated to a position wherein the conductive element 104 does not electrically connect the brush contacts 108 and 124. 1

It will be understood that selective angular rotation of the movable brush contacts 122 and 124 toward their respective fixed brush contacts will effect a longer current pulse duration to the electric motor 148 from the voltage source 146, the maximum pulse duration being achieved when the movable brush contacts are coplanar with their respective fixed brush contacts on the same side of the commutator cylinder 94. Selective adjustment of the movable brush contacts 122 and 124 relative to their respective'fixed-brush contacts 106 and 108 directly'controls the speed and torque of the series wound direct current electric motor 148 and thus the speed of the material handling truck 12 or other apparatus with which the pulse modulating control device is used. While the rotary switch arrangement of H65. 4-6 has been illustrated and described as directly controlling the series wound electric motor 148, the modulated pulses from the rotary switch may be used to selectively trigger silicon controlled rectifiers which in turn control a current input signal to the series wound electric motor 148.

I FIGS. 7 and 8 illustrate the rotary switch means 24 of FIGS.

Land 2 connected in circuit with a direct current electric motor mieanslin a manner to double the current carrying capacity of the rotaryswitch, thereby allowing the use of a means 24 as described above with respect to FIGS. I3 is eliminated and a conventional reversing contactor unit. in-

.dicated generally at reference numeral 160, is utilized to effect reverse rotation of the electric motor.

Referring specifically'to FIG. 7. the rotary switch means 24 is connected in circuit with a direct current voltage source. 146 such that one of the movable brush contact members 48 and one of the fixed position brush contact members 46 are connected in parallel to the positive terminal of the voltage source. The opposite movable brush contact member 48 and opposite fixed brush contact member 46 are connected in parallel to the conventional reversing contact unit 160. The reversing contactor unit 160 includes manually operable switches 162. 164, 166 and 168. Switches 162 and 164 are connected in parallel with each of the switches 162 and 164 being connected to an opposite end of a field coil 170 of a series wound direct current electric motor. The switches 166 and 168 are also connected in parallel to opposite ends of the field coil 170. A conductor 172 connects the switches 166 and 168 to an armature winding 174 of the series wound motor, the armature being also connected to the negative terminal of the DC voltage source 146 to complete the electric motor energizing circuit. Closing switch contacts 162 and 168. with switches 164 and 166 opened, will effect current pulse flow through the field coil 170 in a first direction, while closing switches 164 and 166, with switches 162 and 168 opened, will effect current flow through the field coil in an opposite direction.

As described above with respect to FIGS. 2 and 3, when the movable brush contacts 48 are disposed in a position normal to the plane of the fixed brush contacts 46, as shown in solid lines in FIG. 7, rotation of the cylindrical commutator 40 having conductive elements 54 thereon will not effect current flow through the rotary switch means 24. Angular displacement of the movable brush contacts 48 to a position as shown in dash lines in FIG. 7 will effect current'flow from the DC voltage source 146 through the rotary switch means 24 in parallel paths; each current flow path comprising one of the movable brush contacts 48 and a fixed position brush contact 46 when conductively coupled by a commutator element 54. Such parallel current flow through the rotary switch means 24 allows a larger current pulse to be passed through the rotary switch means thus allowing use of a larger size electric motor. Selective angular displacement of the movable brush contacts 48 establishes the duration of pulse signal through each path established by the rotary switch means 24 and thereby serves to control the torque and rotational speed of the electric motor through controlling the duration of current pulse through the field coil 170 and armature 174 thereof.

FIG. 8 schematically illustrates the rotary switch means 24 connected in circuit with a shunt wound direct current motor,

. movable brush contacts 48 relative to the fixed brush contacts 7 46 serves to modulate the current pulses through the field coil 178 and armature winding 176 of the shunt wound electric motor to thereby control the torque and rotational speed thereof. The direction of rotation of the electric motor may be controlled through the switches 162,, 164, 166 and 168 of the reversing contactor unit 160 in similar fashion to that above described with respect to FIG. 7.

FIG. 9 schematically illustrates the rotary switch means 24 connected in circuit with a compound wound electric motor. The compound wound motor has an armature winding 180, a shunt field coil 1'82 and a series field coil 184. The ends of the series field coil 184 are connected. respectively. to the fixed brush contacts 46 of the rotary switch means 24. The 'armature winding 180 and shunt field coil 182 are connected in parallel with the voltage source 146 and the rotary switch means 24 through the movable brush contacts 48. Angular displacement of the movable brush contacts 48 relative to the fixed brush contacts 46 will vary the duration ofcurrent pulses through the armature 180. the shunt field coil 182 and the series field coil 184. Reversing the direction of angular displaccment of the movable brush contacts 48 rclativc to the neutral position thereof will reverse the direction of current pulses through the series field coil 184. A simultaneous adjustment of the switches comprising the reversing contactor unit will effect a reverse current flow through the shunt field coil 182. thereby reversing the direction of rotation of the compound wound motor.

FIG. 10 schematically illustrates an alternative circuit diagram for a compound wound electric motor similar to that above described with respect to FIG. 9. In the compound wound motor of FIG. 10. the series field coil 184 is connected in series with the direct current voltage source 146 and the movable brush contacts 48 of the rotary switch means 24. The armature winding and shunt field coil 182 are connected in parallel with the rotary switch means 24 through the fixed brush contacts 46. The circuit of FIG. 10 differs from that of FIG. 9 in that reversal of the movable brush contacts 48 relative to their neutral position serves to reverse the direction of current fiow through the armature winding 180 while the conventional reversing contactor unit 160 is employed to reverse the direction of current flow through the shunt field 182 to thereby reverse the direction of rotation ofthe compound motor.

Referring now to FIGS. 1l-13. an alternative embodiment ofa rotary switch device for use in a pulse modulating control arrangement in accordance with the present invention is indicated generally at reference numeral 185; The rotary switch 185 differs from those above described with respect to FIGS. l-6 in that its carbine graphite brush contacts are disposed within an elongated generally annular commutator member as opposed to being radially positioned to engage the outer periphery of the commutator.

The commutator of the rotary switch means185 comprises a hollow cylindrical rotor, indicated generally at 186, preferably formed of four longitudinally extending electrically conductive elements or segments 188 bonded or otherwise suitably fixed in electrically insulated fashion to'nonconductive arcuate segments 190 in alternating fashion to form the annular rotor. The rotor 186 is fixed between end plates 192 and 194 in electrically isolated fashion through bolts 196. The end plate 194 has a central aperture 198 therethrough and a bearing recess 200 formed concentric with the aperture 198 to receive a conventional antifriction bearing 202. The inner race of the bearing 202 receives an elongated tubular shaft 204 therethrough and forms a frictional nonsliding fit thereon.

The aperture 198 is slightly larger than the outer diameter of the tubular shaft 204 to allow rotation of the end plate 194 relative to the shaft 204 through bearing 202.

An outer end portion 206 of the tubular shaft 204 is received within and supported by an end plate 208 which forms an end portion of a cylindrical housing encasing the rotor 186. The end plate 192 of the commutator rotor 186' has an axially extending cylindrical portion 210 received within and rotatably supported by an antifriction bearing 212 disposed within an end plate 214 forming an end portion of the cylindrical housing encasing the rotor. The end plates 208 and 214 are suitably secured together as by bolts 215 to support an annularbaffle section 216 therebetween such that the end plates are disposed in parallel spaced relation. The rotor 186 is thus supported for rotary movement within the cylindrical housing defined by end plates 208, 214 and annular baffle section 216 through bearings 202 and 212. The extending portion 210 of end plate 192 is suitably coupled to a fractional horsepower electric motor (not shown) to provide rotation of the rotor 186 as desired. The end plates 208 and 214 may be secured in supporting relation to a device with which the rotary switch means 184 is to be used through leg portions 218.

A longitudinally extending tubular shaft 220 is disposed within the tubular shaft 204 so as to be rotatably supported therein and has an inner end portion supported by an antifriction bearing 222 within the end plate 192. The tubular shaft 220 has an outer end portion 224 extending outwardly from the end plate 208 to support means for effecting rotation of the shaft, such as a pulley 226. The pulley 226 may be suitably connected to an appropriate hand or foot control, such as the endless belt member 66 illustrated in FlG. l, to allow selective rotation of the tubular shaft 220 relative to tubular shaft 204.

Referring to FIGS. 12 and 13, taken in conjunction with FIG. 11, the hollow fixed position shaft 204 has a pair of axially spaced brush contact holders or guides 226 and 228 fixedly secured to the peripheral surface thereof on opposite sides of the shaft in generally radial relation to the inner peripheral surface of the rotor 186. Each of the brush contact holders 226 and 228 serves to support a carbon graphite conductive brush contact 230 having a generally rectangular cross section, the brush contacts being slidable within their respective brush contact holders and urged outwardly therefrom by suitable coil spring means 232. The outer end portion of each brush contact 230 has a generally arcuate configuration, as viewed in FIG. [2. compatible with the inner peripheral surface of the rotor [86 to establish conducting contact with the conductive elements 188 thereof during rotation of the rotor. Each of the brush contacts 230 has an electrical conductor 234 conductively connected therewith, which conductors are received through suitable apertures in the hollow shafts 204 and 220 and extend outwardly from the outer end 224 of shaft 220. It will be understood that the brush contact holders 226 and 228 are electrically insulated from the shaft 204, or alternatively, that the brush contact holders are made of a nonconducting material.

A pair of brush contact holders 236 and 238 similar to the brush contact holders 226 and 228 are fixedly secured in electrically isolated fashion to the elongated tubular shaft 220 such that upon rotational movement of shaft 220 through pul ley 226, the brush holders 236 and 238 will be angularly displaced relative to the fixed position brush holders 226 and 228. The brush holders 236 and 238 are generally radially supported relative to rotor 186 and serve to slidably receive conductive brush contacts 240 which are spring biased outwardly against the inner peripheral surface of the rotor in similar fashion to the conductive brush contacts 230. Suitable electrical conductors 242 are connected to the brush contacts 240 and extend along the interior of hollow shaft 220 outwardly of the outer end 224 thereof.

The outer peripheral surface of the rotor 186 is preferably provided with cooling fins 244 which serve to centrifugally pump cooling air axially inwardly through suitable apertures 246 in the endplates 208 and 214 and outwardly through 'direct current electric motors therein illustrated. It will be understood that rotational movement of the elongated hollow shaft 220 relative to shaft 204 will efiect angular displacement of the conductor brush members 240 relative to brush contacts 230, thereby modulating current pulses to the electric drive motor through conductive connection'of selected pairs of fixed and movable brush contacts as above described. Rotational movement of the rotor 186 serves to electrically connect the selected pairs of the fixed and movable brush contacts through the conductive elements 188 thereof in similar fashion to the conductive commutator segments 54 above described with respect to FIG. 3.

lt has been found that the rotary switch device illus trated in FIGS. ll-l3 finds ready application where exposed electrical arcing must be eliminated. Further. the heat dissipating features of the last described embodiment facilitate stabilization of the temperature of the outside surfaces of the device only modestly above the ambient air temperature.

While I have shown and described certain preferred embodiments of my invention, it will be obvious to those skilled in the art that changes and modifications may be made therein without departing from the invention in its broader aspects, and therefore the appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of my invention.

lclaim'.

l. A control arrangement for pulse modulation of electrical energy from a direct current voltage source to the armature and field windings of an electric motor, comprising circuit means adapted to selectively electrically connect the electric motor to the voltage source, said circuit means including driven rotary switch means having a rotatable cylindrical commutator and first and second pairs of brush contacts adapted to electrically connect the armature and field windings of the electric motor to the voltage source, said cylindrical commutator having four conductive elements disposed in circumferential spaced relation'about the peripheral surface thereof, said first and second pairs of brush contacts being supported for sliding contact with the peripheral surface of said commutator and said conductive elements, said brush contacts being adapted to modulate pulsed electrical energy therethrough in a first direction to effect torque and speed control of the motor, said first pair of contact members being movable relative to said second pair to modulate pulse electrical energy through said brush contacts in a direction reversed from said first direction to effect torque and speed control of the motor in a reverse direction of rotation.

2. A control arrangement as defined in claim 1 wherein the circumferential space between adjacent conductive elements is greater than the circumferential width of the contact surfaces of said brush contacts.

3. A control arrangement according to claim 1 wherein said brush contacts are adjustable to reverse the direction of electrical pulses in the motor field windings while maintaining the initial direction of electrical pulses through the armature windings of the motor.

4. A control arrangement according to claim I wherein said brush contacts are adjustable to reverse the direction of electrical pulses in the armature of the electrical motor while maintaining the initial direction of electrical pulses through the field windings of the motor.

5. A control arrangement according to claim 1 wherein said movable pair of brush contacts is movable to a position wherein the electric motor is in open circuit with the voltage source.

6. A pulse control arrangement as defined in claim 1 wherein the voltage source, the armature and field windings of the motor, and said rotary switch means are connected in elec-' trical series, said fixed and movable brush contacts being electrically connected in circuit such that electrical energy may follow parallel paths through said rotary switch means.

7. A rotary switch comprising a cylindrical hollow rotatable commutator having longitudinally extending conductive elements supported thereon with conducting surfaces lying in the internal peripheral surface of said commutator, means supporting said commutator for rotary movement, and fixed and movable brush contacts supported within said hollow commutator on fixed and movable shafts disposed generally axially of the commutator for intermittent contact with said conductive surfaces in the internal peripheral surface of said commutator, said conductive elements being adapted to conductively connect selected pairs of said fixed and movable brush contacts during rotation of said commutator, said movable brush contacts being movable relative to said fixed brush contacts in a manner to vary the duration of conductive connection between said fixed and movable brush. contacts during rotation of said commutator.

8. A rotary switch as defined in claim 7 wherein said conductive elements are circumferentially spaced about said cylindrical commutator.

9. A rotary switch as defined in claim 8 wherein said brush contacts are disposed in generally radial relation to the inner peripheral surface of said commutator for sliding contact therewith.

said fixed brush contacts.

II. A rotary switch as defined in claim 7 wherein said commutator includes cooling fins disposed about the outer peripheral surface thereof.

12. A rotary switch as defined in claim 7 wherein said means supporting said commutator for rotary movement comprises a housing encasing said commutator.

13. A rotary switch as defined in claim 12 wherein said housing includes air flow apertures therein. and wherein said commutator includes cooling fins disposed about the outer peripheral surface thereof, said cooling fins being adapted to effect air flow through said housing apertures and about said commutator. 

1. A control arrangement for pulse modulation of electrical energy from a direct current voltage source to the armature and field windings of an electric motor, comprising circuit means adapted to selectively electrically connect the electric motor to the voltage source, said circuit means including driven rotary switch means having a rotatable cylindrical commutator and first and second pairs of brush contacts adapted to electrically connect the armature and field windings of the electric motor to the voltage source, said cylindrical commutator having four conductive elements disposed in circumferential spaced relation about the peripheral surface thereof, said first and second pairs of brush contacts being supported for sliding contact with the peripheral surface of said commutator and said conductive elements, said brush contacts being adapted to modulate pulsed electrical energy therethrough in a first direction to effect torque and speed control of the motor, said first pair of contact members being movable relative to said second pair to modulate pulse electrical energy through said brush contacts in a direction reversed from said first direction to effect torque and speed control of the motor in a reverse direction of rotation.
 2. A control arrangement as defined in claim 1 wherein the circumferential space between adjacent conductive elements is greater than the circumferential width of the contact surfaces of said brush contacts.
 3. A control arrangement according to claim 1 wherein said brush contacts are adjustable to reverse the direction of electrical pulses in the motor field windings while maintaining the initial direction of electrical pulses through the armature windings of the motor.
 4. A control arrangement according to claim 1 wherein said brush contacts are adjustable to reverse the direction of electrical pulses in the armature of the electrical motor while maintaining the initial direction of electrical pulses through the field windings of the motor.
 5. A control arrangement according to claim 1 wherein said movable pair of brush contacts is movable to a position wherein the electric motor is in open circuit with the voltage source.
 6. A pulse control arrangement as defined in claim 1 wherein the voltage source, the armature and field windings of the motor, and said rotary switch means are connected in electrical series, said fixed and movable brush contacts being electrically connected in circuit such that electrical energy may follow parallel paths through said rotary switch means.
 7. A rotary switch comprising a cylindrical hollow rotatable commutator having longitudinally extending conductive elements supported thereon with conducting surfaces lying in the internal peripheral surface of said commutator, means supporting said commutator for rotary movement, and fixed and movable brush contacts supported within said hollow commutator on fixed and movable shafts disposed generally axially of the commutator for intermittent contact with said conductive surfaces in the internal peripheral surface of said commutator, said conductive elements being adapted to conductively connect selected pairs of said fixed and movable brush contacts during rotation of saiD commutator, said movable brush contacts being movable relative to said fixed brush contacts in a manner to vary the duration of conductive connection between said fixed and movable brush contacts during rotation of said commutator.
 8. A rotary switch as defined in claim 7 wherein said conductive elements are circumferentially spaced about said cylindrical commutator.
 9. A rotary switch as defined in claim 8 wherein said brush contacts are disposed in generally radial relation to the inner peripheral surface of said commutator for sliding contact therewith.
 10. A rotary switch as defined in claim 7 including means for selectively moving said movable brush contacts relative to said fixed brush contacts.
 11. A rotary switch as defined in claim 7 wherein said commutator includes cooling fins disposed about the outer peripheral surface thereof.
 12. A rotary switch as defined in claim 7 wherein said means supporting said commutator for rotary movement comprises a housing encasing said commutator.
 13. A rotary switch as defined in claim 12 wherein said housing includes air flow apertures therein, and wherein said commutator includes cooling fins disposed about the outer peripheral surface thereof, said cooling fins being adapted to effect air flow through said housing apertures and about said commutator. 